Active Signal Technologies, in partnership with the Brain Attack Team of the University of Maryland Medical Center, proposes to refine and test a novel portable, non-invasive system that will enable rapid identification of stroke. Approximately 750,000 people suffer a stroke each year and over 80% of these are ischemic. Yet only 1% of this number receives medical treatment such as TPA that is known to dissolve clots and promote favorable outcome if administered within 3 hours of onset. Among the many causes of this serious health and ultimately economic problem is the inability to rapidly differentiate ischemic from hemorrhagic strokes to allow intervention. The device is a small non-invasive system that measures the acoustic signature of the brain and compares it with the patient's arterial waveform. Active Signal will add code to calculate those signal features identified in Phase I as indicative of the patient's stroke condition, and the team will clinically test on 200 patients the hypotheses for stroke identification determined in Phase I. The system will be miniaturized for EMS units to use at the scene of injury. This would significantly increase the percentage of ischemic stroke patients who would receive time-sensitive therapies, reducing disability and medical costs.